1. Field of the Invention
The invention is in the field of devices for the fabrication of corrugated cardboard.
2. Brief of Description of the Background Art
The invention relates to a pressure plate arrangement for joining together a plurality of material webs each comprising at least one plain web and/or at least one corrugated web, to form a corrugated cardboard web. At least one of the material webs is provided with adhesive at least in sections. The arrangement comprises a contact pressure unit provided with a pressure plate, and a heatable counter pressure plate, between which the material webs to be joined are passed. The contact pressure unit and the pressure plate are provided with means to vary their separation from the counterpressure plate.
Pressure plate arrangements of this kind are known from the prior art. For example, the brochure "The Double-Facer Group", Brochure No. 2 (694G) 0.5 of Messrs Peters Maschinenfabrik GmbH, describes an arrangement of this kind on Page 10. In this arrangement, the material webs provided with adhesive, contact the heatable counterpressure plate and are pressed against one another from the opposite side by means of the pressure plates. The supply of heat via the heatable counterpressure plate accelerates curing of the adhesive. Of course in the case of multi-layer corrugated cardboard webs, i.e. corrugated board webs having two or more webs (e.g. double-wall corrugated cardboard), the problem arises that the temperature in the corrugated board decreases with increasing distance from the heated counterpressure plate, so that complete drying of the adhesive points remote from the counterpressure plate takes a relatively long time. To counteract this problem, in the case of moving material webs it is either necessary to appropriately reduce the speed of movement in order to allow adequately long heat treatment of the adhesive locations, or else it is necessary to appropriately lengthen the heatable counterpressure plate. Alternatively, it is necessary to appropriately increase the amount of heat supplied per unit of time. Thus, the required heat treatment expense increases with increasing corrugated board thickness and/or increasing weight per unit area.
Of course there are economic and practical limits both to reducing the speed of movement of the material web, to lengthening the apparatus, and also to increasing the amount of heat supplied per unit of time via the counterpressure plate. It is, therefore, an object of this invention to realize a pressure plate arrangement of the above type whereby the adhesive curing process can be accelerated for the same speed of movement, the same apparatus length and the same heat supply via the counterpressure plate.